1. Field of the Invention
The present invention relates to the field of the control of linear products of very great length relative to their other dimensions, namely of products in the form of filaments, yarns, ribbons or cloth and has for its object a detector for the contactless measurement of the morpho-dimensional and dynamic characteristics of such a product on a production machine or the like.
2. Description of the Related Art
The knowledge of the characteristics of a product in the form of filament, yarn, ribbon or cloth is particularly necessary in the field of spinning for the verification of the regularity of a given product, namely to detect the possible defects due either to malfunction of the machine or to defectiveness of an element of the machine, or to irregularity or non-homogeneity of the material itself that is used, namely, the filament, yarn, ribbon or cloth.
Moreover, in the field of weaving textile filaments or the like or also in the field of winding metallic wires, there is also a problem of instantaneous recognition of the characteristics of said filaments, particularly their tension and/or their speed and/or their torsion and/or their regularity.
This knowledge of the characteristics of the linear products is particularly applicable to all the sectors of the textile industry, such as spinning, spinning synthetic fibers, winding, warping and weaving.
At present, the measurements of the essential characteristics of the linear products of this type are generally effected by mechanical, electrical or electromagnetic means, by contact, namely, for measurement of speed, at least one wheel mechanism connected to a counter, and as to the tension, by means of a wheel device mounted on a tensioned arm connected to a weighing device.
These known means, however, have the drawback of being in contact with the filament, of needing a wheel, of passing the filament along a sinuous path with the need to tension it, which induces friction, bending, torsion, etc. . . . , and thus imposing supplemental parasitic tensions on said filament.
Moreover, these known means can lead to the formation of fluff and dust and modify the characteristics of the product by friction and heating.
Finally, it is also possible that, upon a breakdown of the machine or the elements of the machine, or even of the measuring detector itself from fluff and dust, to produce blockages of the product to be measured or to be controlled and/or the adhesives of the materials by adherence or fusion (in the case of high speeds), because of the material constituting the product to be measured or the chemical products used for producing the filament, such as textile oil for example.
At present, for example, the measurement of the torsion is possible only by withdrawing and destructive testing of specimens. Such a measurement is not possible on a product in movement. Similarly, the measurement of the fundamental characteristics of a product of great length, such as a textile filament, for example in movement, which are the speed and tension, cannot be effected at present other than by placing a detector in contact with the product, as indicated above.
It is also known to effect measurements of the regularity of the mass or size, for example of filaments, by means of capacitative or optical detectors permitting, in this case, to effect contactless measurements either on the production means, or on specific machines, for example laboratory apparatus.
Thus there is known, from FR-A-2 549 096, a process for automatic control of textile filaments and an apparatus for practicing this process, permitting automatically effectuating, with the aid of a single and same apparatus, a group of measurements on at least one sample of filament, these measurements being conceived to permit at least one determination of the titer of this filament and a determination of its regularity as to linear mass, and/or at least one determination of the torsion and a determination of the dynamometric properties of this filament. According to this reference, the measurements are repeated on a series of specimens of the same filament and the results are registered, then processed by computer means, for their statistical use and/or their storage.
According to this process and the apparatus for its practice, the measurement of the regularity of the filament is effected by means of a capacitative detector comprising a double condenser comprising a central plate and two lateral plates defining two interstices of which one is traversed by the filament. This process and this apparatus permit obtaining information relative to the regularity of the filament thanks to the capacitative detector and of the titer of this filament thanks to a balance of precision compiling said filament after measurement of its regularity.
From FR-A-2 587 806 is known a device for the continuous measurement of the linear mass of a textile product present in the form of a detector analogous to that for practicing the process according to FR-A-2 549 096, in which are provided means simultaneously modifying the air gap of the two capacitances (condensers) constituting said detector. This detector permits a more precise measurement than earlier detectors.
The capacitative detector measures the mass regularity of the filament, given that the variation of the mass in the air gap of the capacitative detector gives rise to a variation of the dielectric of the condenser formed by the two armatures of this detector, in which the dielectric is constituted by the ambient air and the mass of filament situated between the armatures.
There is also known, from FR-A-2 651 888, a process and an apparatus permitting the characterization and the measurement of the quality of ribbons and yarns or of the filaments of textile fibers.
This process and this device also consist in using specimens and effecting on these latter measurements of regularity, of the breakage force of these specimens, as well as the determination of the titer of said specimens. Such a device permits of course characterizing rapidly a large number of specimens, but it is not at all adapted to continuous measurement, simply because of its construction and the measurement means used. Moreover, the assembly of detectors does not permit determining the speed and the tension of the filament.
Furthermore, in known detectors, it is usual to provide an adjustability of the frequency supply of the capacitance or capacitances as a function of certain physico-chemical parameters, such as humidity.
FR-A-2 657 959 describes a process and a device for the measurement of torsion of a textile filament, in which the filament is illuminated by optical means from a luminous beam, so as to form an illuminated spot corresponding to the light diffracted by the fibers from the surface of the core, this luminous spot being examined so as to analyze the energy distribution so as to define the angle of torsion.
Finally, there is known from FR-A-2 657 958 a process and a device for the measurement of at least one transverse dimension of a textile filament, said process consisting in illuminating the filament with a coherent light beam, examining the interference fringes obtained in the focal plane of an optical system, and deducing the transverse dimension of the distance separating the interference fringes, at least two symmetrical fringes being provided relative to the filament to form two secondary interfering sources, the transverse dimension of the filament being deduced from the spacing between the fringes of the obtained interference figure.
This known process and device permit determining particularly the number of a filament, but, because of the necessary size of the device and its mounting about the filament to be measured, its application to continuous measurement on a production machine or for temporary measurement at the inlet or at the outlet of such a machine cannot be envisaged.
If the recited means permit measurements of regularity and torsion without contact and if, by severe miniaturization, the realization of these measurements were permitted without contact on production machines, none of these means would permit simultaneous contactless measurement of the speed of a linear product, of its mass regularity, absolute or not, of its tension, or of its torsion.
Furthermore, the publication MELLIAND TEXTILBERICHTE, Vol. 73, No. 8, August 1992, HEIDELBERG, pages 611-613, XP294573--LEUENBERGER "Fadenspannungen beruhrungslos ermitteln" describes a technique for measurement of the tension of a continuous filament to be spun, by measurement of the circular vibration of the filament relative to a guide eyelet for the filament. This measurement is particularly difficult to carry out, because the filament follows a spacial trajectory of large amplitude, such that the addition of a tension detector with loading is inconceivable. The filament is subjected to a circular vibration which causes the appearance of a loop and a node on the forming filament, such that at this region the filament is fragile and the installation of a detector cannot be envisaged.
The circular oscillations of the filament are registered by means of a camera and the vibration node is determined from the curve of the envelope extracted from the registry of said oscillations.
According to this document, the filament is not subjected to any external vibration, the vibration being generated in the course of operation of the machine. The detector considers this vibration and, after processing, deduces from it the tension. However, this detector is not capable of extracting the component of vibration of a filament, even if it is minimal, without contact and displacement of the filament.